Exhaust temperature based control strategy for balancing cylinder-to-cylinder fueling variation in a combustion engine

Abstract

The present disclosure provides a control strategy for balancing injector-to-injector fueling variations for a combustion engine having multiple combustion chambers (and cylinders), with multiple individually actuated injectors for injecting fuel into the combustion chambers, wherein at least one injector is assigned to each combustion chamber and a common rail supplies fuel to the multiple injectors. The method includes changing the actuation waveform of an injector assigned to a combustion chamber having an exhaust gas temperature deviating by more than the predetermined value from the average exhaust gas temperature, in order to change the amount of fuel injected.

1. A method for controlling a combustion engine including multiple combustion chambers, and multiple, individually-actuated injectors for injecting fuel into the combustion chambers, wherein at least one injector is assigned to each combustion chamber, and wherein the combustion engine further includes a common rail for supplying fuel to multiple injectors, the method comprising:
 actuating the injectors in accordance with a requested fueling map, the actuation being associated with an unchanged actuation according to the requested fueling map; 
 monitoring an exhaust gas temperature of each combustion chamber; 
 determining an average exhaust gas temperature of the combustion chambers; 
 determining whether the exhaust gas temperature of the combustion chamber deviates by more than a predetermined value from the average exhaust gas temperature; and 
 changing actuation of the injector assigned to the combustion chamber having exhaust gas temperature deviating by more than the predetermined value from the average exhaust gas temperature in order to change an amount of fuel injected, and limiting to a predetermined maximum the number of changes away from the unchanged actuation according to the requested fueling map for each injector. 
 
   
   
     2. The method according to  claim 1 , wherein the predetermined value is a predetermined percentage of the average exhaust gas temperature. 
   
   
     3. The method according to  claim 1 , wherein the predetermined value of the temperature deviation lies between 10° C. and 30° C. 
   
   
     4. The method according to  claim 3 , wherein the predetermined value of the temperature deviation is approximately 20° C. 
   
   
     5. The method according to  claim 1 , wherein the value of each change is a predetermined value. 
   
   
     6. The method according to  claim 1 , wherein changing actuation is associated with a change to an actuation waveform, and the overall value of the change to the actuation waveform of a respective injector is limited. 
   
   
     7. The method according to  claim 5 , wherein changing actuation is associated with a change to an actuation waveform, and the value of each change or the overall value of the change to the actuation waveform of each respective injector is specified as a percentage of the unchanged actuation waveform. 
   
   
     8. The method according to  claim 7 , wherein the total value of the change to the actuation waveform of the respective injector is limited to 10%. 
   
   
     9. The method according to  claim 1 , wherein the method is repeated cyclically. 
   
   
     10. The method according to  claim 9 , wherein changing actuation is associated with a change to an actuation waveform, and following a change to the actuation waveform of an injector, a predetermined period of time elapses before the method is repeated cyclically, the predetermined period of time being longer than a normal period of time between cyclical repetitions. 
   
   
     11. The method according to  claim 1 , wherein changing actuation is associated with a change to an actuation waveform, and including recording settings for changes in the actuation waveform of an injector. 
   
   
     12. The method according to  claim 11 , wherein the change settings are maintained when the combustion engine is restarted. 
   
   
     13. The method according to  claim 11 , wherein the change settings are reset when the combustion engine is restarted. 
   
   
     14. The method according to  claim 1 , further including determining whether the exhaust gas temperature of a combustion chamber deviates by more than a maximum predetermined value from the average exhaust gas temperature, the maximum predetermined value being greater than the acceptable predetermined value, and issuing a warning signal if there is a deviation which is greater than the maximum predetermined value. 
   
   
     15. The method according to  claim 6 , wherein the value of each change or the overall value of the change to the actuation waveform of each respective injector is specified as a percentage of the unchanged actuation. 
   
   
     16. The method according to  claim 15 , wherein the total value of the change to the actuation waveform of a respective injector is limited to 10%. 
   
   
     17. The method according to  claim 15 , wherein the total value of the change to the actuation waveform of a respective injector is limited to 5%. 
   
   
     18. The method according to  claim 8 , wherein the total value of the change to the actuation waveform of a respective injector is limited to 5%. 
   
   
     19. The method of  claim 1 , wherein changing actuation is associated with a change to an actuation waveform, and changing actuation includes, using a small percentage of the fueling from actuation of the injectors in accordance with the requested fueling map, for incremental changes of the injector actuation waveform. 
   
   
     20. The method of  claim 1 , including an associated cylinder for each combustion chamber, and including allowing for a predefined cylinder exhaust gas temperature offset due to cylinder location. 
   
   
     21. A system for controlling a combustion engine including a plurality of combustion chambers, and a plurality of individually actuable injectors configured to inject fuel into the combustion chambers, wherein at least one injector is assigned to each combustion chamber,
 the system comprising a control unit configured to perform a series of steps, the steps including:
 actuate each injector to inject fuel into associated combustion chambers in accordance with a request profile; 
 monitor an exhaust gas temperature of each combustion chamber; 
 determine an average exhaust gas temperature of the combustion chambers; 
 determine whether the exhaust gas temperature of the combustion chamber deviates by more than a predetermined value from the average exhaust gas temperature; 
 change actuation of the injector of an associated combustion chamber having exhaust gas temperature deviating by more than the predetermined value from the average exhaust gas temperature, in order to change an amount of fuel injected; and 
 wait a predetermined period of time following a change to the actuation waveform of an injector, then repeat the steps cyclically, the predetermined period of time being longer than a normal period of time between cyclical repetitions. 
 
 
   
   
     22. The system of  claim 21 , wherein the control unit is configured to change actuation of the injector assigned to the combustion chamber having exhaust gas temperature deviating by more than 30° C. from the average exhaust gas temperature. 
   
   
     23. The system of  claim 21 , wherein the control unit is configured to limit the number of changes away from the unchanged actuation according to the request profile for each injector to a predetermined number of changes. 
   
   
     24. The system of  claim 21 , wherein the control unit is configured to record settings for changes in actuation of the injector, and either to maintain change settings when the combustion engine is restarted, or to reset the change settings when the combustion engine is restarted. 
   
   
     25. The system of  claim 21 , wherein the control unit is further configured to determine whether the exhaust gas temperature of a combustion chamber deviates by more than a further predetermined value from the average exhaust gas temperature, the further predetermined value being greater than the predetermined value, and to issue a warning signal if there is a deviation which is greater than the further predetermined value. 
   
   
     26. A combustion engine including:
 a plurality of combustion chambers; 
 at least one injector associated with each of the plurality of combustion chambers and configured to inject a quantity of fuel into an associated combustion chamber in accordance with a request profile; and 
 a control unit configured to change the quantity of fuel injected by the at least one injector in response to a deviation of exhaust gas temperature from the associated combustion chamber by more than a predetermined value from an average exhaust gas temperature of all of the plurality of combustion chambers, and determining whether the exhaust gas temperature of a combustion chamber deviates by more than a maximum predetermined value from the average exhaust gas temperature, the maximum predetermined value being greater than the acceptable predetermined value, and issuing a warning signal if there is a deviation which is greater than the maximum predetermined value. 
 
   
   
     27. The engine of  claim 26 , further including:
 an exhaust gas line associated with each of the plurality of combustion chambers; and 
 a respective temperature sensor associated with each of the exhaust gas lines and configured to determine the exhaust gas temperature of the associated combustion chamber. 
 
   
   
     28. The engine of  claim 27 , further including:
 a common exhaust gas line receiving exhaust gas from the exhaust gas lines associated with the plurality of combustion chambers; and 
 a temperature sensor associated with the common exhaust line and configured to measure an average exhaust gas temperature of all of the combustion chambers. 
 
   
   
     29. The engine of  claim 26 , further including:
 a common rail for supplying fuel to the at least one injector associated with each of the plurality of combustion chambers.